James Webb Space Telescope completes risky sunshield deployment


In letter: The James Webb Space Telescope has successfully deployed its five-layer, 70-foot sunshield, checking off a critical make-or-break step in the observatory’s multi-phase, post-launch prep as it continues its journey towards the L2 insertion point.

The unfolding and tensioning of the sunshield took place over the course of eight days, involving 139 of Webb’s 178 release mechanisms as well as 70 hinge assemblies, eight deployment motors, 90 individual cables and roughly 400 pulleys.

If that sounds daunting, consider this: the James Webb Space Telescope has 344 so-called single point failures, or individual steps that must work without incident. If any one point fails – a cable gets stuck or a release mechanism doesn’t trigger – the whole project could be in jeopardy.

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The sunshield will protect the telescope from light and heat from the Sun, Earth and Moon. Each layer is about as thin as a human hair, but collectively, they’ll be able to reduce exposure from the Sun from more than 200 kilowatts of solar energy down to just a fraction of a watt. That’ll be crucial in keeping the scope nice and chilly for optimal operation.

Things have been going swimmingly thus far, but Webb isn’t out of the woods yet. It’ll be another five-and-a-half months before the observatory delivers its first images. Between now and then, Webb must deploy its secondary mirror and primary mirror wings, calibrate its science instruments and align its telescope optics.

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Interested parties can follow the telescope’s journey through space over on NASA’s website. As of this writing, Webb is approximately 593,000 miles from Earth and has another 305,000 miles to travel before it reaches its target orbit. Deployment of the secondary mirror begins today.



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